In a known manner, the base plate includes a ventilation filter and at least one rivet blank projecting from the plate. Said at least one rivet blank is intended to penetrate the printed circuit and to be deformed for rigidly connecting the printed circuit to the base plate. Said at least one rivet blank projects from a face of the plate. The ventilation filter includes a ventilation opening.
The ventilation filter function, also called a breather, borne by a base plate of a case housing a printed circuit is provided by a specific shape produced on the base plate. A so-called breathable membrane is stuck on a shape stamped into the base plate of the case, then covered by a protective member, advantageously a label with the four corners thereof bored through.
The base plates of an electronic case are generally produced by stamping. These base plates have one or more rivet blanks that are precursors of a respective rivet intended to fix, by riveting, a printed circuit to the base plate. The printed circuit is frequently in the form of an electronic board.
The rivet blanks and then the formed rivets can, for example, be placed on the perimeter of the base plate while being evenly distributed in order to provide the isostatism of the assembly formed from the printed circuit and the base plate, the printed circuit being linked to an electrical connector by being incorporated in a protective case comprising such a base plate.
One of the difficulties of forming a base plate of such a case is the production of rivet blanks, then the riveting operation. The formation of the rivet blanks by stamping, then of the rivets by deformation of the blanks should be carried out progressively in successive steps. This requires various levels of depth about each rivet blank.
It is normally preferred to place the rivet blanks on a base plate in areas covered with a thermal material and known as a thermal platform or in stamping areas. Thus, the material of the rivet blanks is less stressed and the risks of having cracks is reduced. As a result, it is relatively rare to have a rivet in the middle of the base plate of the case in a flat area.
Another difficulty associated with riveting is the pressing of the rivet blank in order to deform it when assembling the printed circuit on the base plate, which is frequently made of aluminum. The initial shape of the rivet blank is decisive as is the pressure force and the shape of the tools which press on the rivet blank in order to deform it.
The faults occurring during this riveting process can be cracks or an excessive material thickness reduction. It is important to eliminate these faults in order to ensure sealing of the case and, consequently, of the computer as an assembly comprising the case and the circuit incorporated in the case.
During the design of a printed circuit, particularly in the form of an electronic board, it is necessary to take into account the future locations of the rivets and the geometry associated with the ventilation filter function. Indeed, in these areas there must not be electronic components which collide either with the base plate or with the equipment used for assembling, for example the tools for deformation by pressing the rivet blanks in order to form the rivets.
These areas are therefore restrictive with regard to the placement of the components and of the electronic tracks on the printed circuit. Therefore, it is sometimes complicated to develop a printed circuit configuration that is compatible with the size of the case which must be as small as possible as is frequently required.
The problem underlying the present invention is, for an assembly of a protective case and printed circuit housed in the case comprising a base plate, this base plate comprising a ventilation filter and at least one rivet blank for holding the printed circuit with respect to the base plate, to position the rivet blank on an area of the base plate, firstly, corresponding during the riveting operation to an area of the printed circuit which is free of any electronic component and, secondly, which is suitable for implementing a riveting method that does not cause cracks on the rivet formed in this manner.